1. Field of the Invention
Apparatuses and methods consistent with the present invention are generally directed to Bluetooth, and more specifically, to a routing system and method for transmitting data between devices forming a Bluetooth network.
2. Description of the Related Art
With the advent of various telecommunication devices such as personal computers (PCs), mobile phones, and personal digital assistances (PDAs), interconnections are needed for telecommunication devices and new technologies have been proposed for data communications. Bluetooth, whose promoters include ERICSSON (Sweden), IBM and INTEL (U.S.A), NOKIA (Finland), and TOSHIBA (Japan), is featured to implement short-range data communications of telecommunication devices using radio waves, which was previously implemented using (wired) cable connection or infrared transmission.
Bluetooth uses a high radio frequency of 2.4 GHz to enable communications over obstacles, provides a data transfer rate of 1˜10 Mbps, and covers a transfer distance of 10˜100 m, which is superior to the Infrared Data Association (IrDA) standard. In addition, Bluetooth consumes lower amounts of power while performing high data rate transmission and ensures security for the data transmission.
FIG. 1 illustrates a conventional Bluetooth system. In general, the Bluetooth system provides a point-to-point connection or a point-to-multipoint connection. In the point-to-multipoint connection, a plurality of Bluetooth devices shares a same channel. At least two of the Bluetooth devices sharing the same channel, form a piconet. One Bluetooth device, which initiates communication in the piconet, operates as a master, and the other Bluetooth devices operate as slaves. The master controls channel access of the slaves. A plurality of piconets having at least one overlapping service area, form a scatternet. A master device in a certain piconet may operate as a slave in another piconet. FIG. 1 illustrates a construction of the scatternet.
Referring to FIG. 1, thee piconets A, B, and C form a scatternet. A master of each piconet A, B, and C is a first device 100, a first device 110, and a first device 120, respectively. The first device 100, which is the master of the piconet A, also operates as a slave of the piconet B. This double-role property enables extension of communications into other piconets, which was limited in the conventional piconet. The master 100 of the piconet A is connected with the master 110 of the piconet B, and the slave 116 of the piconet B is connected with the master 120 of the piconet C. A routing process is described below for transferring data from a device of the piconet A to a device of the piconet C.
In general, the route for transferring data between devices of different piconets includes four processes, that is, an inquiry process, a page process, a routing request process, and a routing response process, which are described in detail below.
The inquiry process is to recognize addresses of unknown neighbor devices when a device of a piconet attempts to connect to any other device. The piconet device inquires about the information and address of radio resource used for other devices. The inquired devices send to the inquirer device the information and address of its radio resource. FIG. 2 illustrates packet transmission at the inquiry process. To perform the inquiry process, a transmitter device broadcasts packets to other devices at a certain interval. Specifically, the transmitter device sends the packets in a packet transmit period (TX) and receives a response for the transmitted packets in a packet receive period (RX). The TX and the RX generally have the same size and alternate with each other. The TX is 625 bits long, of which two 68 bits are used by the transmitter device to broadcast its information to other devices as shown in FIG. 2. The transmitter device broadcasts the packets using the usable radio resource to probe a radio resource used by other devices (receiver devices).
The page process is to set a master among the devices of the piconet. The master is a specific device among the piconet devices sharing the information and address of the radio resource through the inquiry process. The master pages the piconet devices one by one. Through the page process, the piconet devices are divided into a master and a slave.
The routing request process is to request a route from a source device to a destination device. The source device generates and broadcasts a route request (RREQ) message to adjacent devices. The RREQ-received device compares its address information with that of the destination device embedded in the RREQ message. If the two address information are different, the RREQ-received device updates and broadcasts the RREQ message to the adjacent devices. If the two address information are the same, the RREQ-received device recognizes that it is the device to which the source device attempts to transmit data. The data transmissions between the devices of one piconet generally need not follow the above processes since the master knows all the address information of the slaves in the piconet. That is, the slave can route to another slave through the master.
The routing response process is to transmit a response for the routing request from the destination device to the source device. Through the routing response process, the route is established between the source device and the destination device for data transmission. The destination generates and sends a route reply (RREP) message to the source device using the route of the RREQ message.
In light of the foregoing, all the devices of the piconet or the scatternet are involved with the routing from the source device to the destination device for data transmission. The routing time is delayed due to the inquiry and page processes. Conventionally, the inquiry process takes 10.24 seconds, and the page process with respect to one device takes 0.64 seconds. Accordingly, the inquiry and page processes take 14.72 seconds in the piconet including one master and seven slaves.
FIG. 3 illustrates a packet transmission process from the source device to the destination device, in which a route is positioned wherein masters and slaves are disposed in an alternating manner. It is assumed that a source device and a first device form a piconet A, and the first device and a second device form a piconet B.
Upon receiving packets from the source device of the piconet A, the first device needs to change to a radio resource used in the piconet B in order to transmit the packets to the second device. After changing to the radio resource of the piconet B, the first device transmits the packets to the second device. As shown in FIG. 3, a time slot of the piconet A and that of the piconet B are assigned differently from each other. Hence, the first device uses the time slot of the piconet A to receive the packets from the source node, and uses that of the piconet B to transmit the packets to the second device. That is, the first device cannot transmit the packets, which are received from the source device, to the second device immediately afterwards, but transmits the packets with delay for a certain amount of time.